BOSTON — The police sergeant President Obama accused of acting "stupidly" in arresting a Harvard professor offered his own account of the incident Thursday.

The arrest of the professor, Henry Louis Gates Jr., was dominating talk shows and dinner conversations even before Obama discussed it Wednesday.

But the president's comments seemed to further polarize debate over whether the sergeant, James Crowley, was right to arrest Gates for disorderly conduct while investigating a possible break-in at the professor's home in Cambridge, Mass.

Police unions and other law-enforcement groups lined up behind Crowley on Thursday, calling his actions justified, while the Congressional Black Caucus called on Congress to address the issue of racial profiling.

Commissioner Robert Haas of the Cambridge Police Department said he would convene an independent panel to investigate the incident, but added that his officers were "deeply pained" by Obama's comments and that Crowley had followed protocol.

The dispute between Gates and Crowley centers on two things: which one treated the other rudely and whether they properly identified themselves.

Gates, 58, says the sergeant repeatedly refused to reveal his name or badge number; Crowley, 42, says the professor initially refused to provide identification, then produced only his Harvard ID card, which included no address, to prove he lived in the house.

Crowley told a local radio station Thursday that Obama "didn't know all the facts" and that Gates — a prolific scholar of African-American history and a leading intellectual — had been oddly belligerent from the start of their encounter July 16.

"From the time he opened the door it seemed that he was very upset, very put off that I was there in the first place," Crowley said.

Crowley's visit to the professor's home near Harvard Square was prompted by a 911 call from a passer-by who reported two black men trying to force open the front door. The men were Gates, just home from a trip to China, and his cabdriver; Gates said this week that his door was jammed and he had asked the driver for help shoving it open.

After getting in, Gates said, he saw Crowley on his porch. The sergeant was disrespectful from the beginning, the professor said, asking him to step outside without explanation and demanding identification while refusing to provide his own name or badge number.

Crowley said he tried to identify himself several times but the professor was shouting too loudly to hear.

"He was arrested after following me outside the house," Crowley said on the radio, "continuing the tirade even after being warned multiple times, probably a few more times than the average person would have gotten."

The president commented on the matter again Thursday. In an interview with ABC News for "Nightline," Obama said he was "surprised by the controversy surrounding my statement because I think it was a pretty straightforward commentary that you probably don't need to handcuff a guy, a middle-aged man who uses a cane, who's in his own home."

He said he had heard Crowley was an "outstanding police officer," but added that with all that is going on in the country, "it doesn't make sense to arrest a guy in his own home if he's not causing a serious disturbance."

The police dropped disorderly conduct charges against Gates on Tuesday.

Crowley, an 11-year veteran of the department, was hand-picked to teach a class on racial profiling at a police training academy.

Thomas Fleming, director of the police academy at the Lowell Police Department, said Crowley has taught the course for five years.